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In class-based, object-oriented programming, a constructor (abbreviation: ctor) is a special type of function called to create an object.It prepares the new object for use, often accepting arguments that the constructor uses to set required member variables.
The Math object contains various math-related constants (for example, π) and functions (for example, cosine). (Note that the Math object has no constructor, unlike Array or Date. All its methods are "static", that is "class" methods.) All the trigonometric functions use angles expressed in radians, not degrees or grads.
data variable type ref to class . create object variable ... JavaScript (ES6) constructor ... TYPE): TYPE assign set_item do instructions end set_item (value: TYPE; ...
In object-oriented programming, a class defines the shared aspects of objects created from the class. The capabilities of a class differ between programming languages , but generally the shared aspects consist of state ( variables ) and behavior ( methods ) that are each either associated with a particular object or with all objects of that class.
In class-based programming, a factory is an abstraction of a constructor of a class, while in prototype-based programming a factory is an abstraction of a prototype object. A constructor is concrete in that it creates objects as instances of one class, and by a specified process (class instantiation), while a factory can create objects by instantiating various classes, or by using other ...
Notably, a constructor is a class method as there is no object (instance) available until the object is created, but destructors, initializers, and finalizers are instance methods. Further, constructors and initializers often can accept arguments, while destructors and finalizers generally do not as they are often implicitly callable.
In the above UML class diagram, the Creator class that requires a Product object does not instantiate the Product1 class directly. Instead, the Creator refers to a separate factoryMethod() to create a product object, which makes the Creator independent of the exact concrete class that is instantiated.
When a class constructor does not explicitly call the constructor of one of its object-valued fields in its initializer list, the default constructor for the field's class is called. In the standard library, certain containers "fill in" values using the default constructor when the value is not given explicitly.